Flexible tubular casing



July 6, 1937. 6:. FISCHER I FLEXIBLE TUBULAR CASING Filed Nov. 25, 1936 INVENTOR CHAQLES FISCHER ATTORNEY Patented July 6, 1937 s'rss 12 Claims.

This invention relates to flexible metal casings, and particularly to that type used for housing flexible shafts, radio remote controls, and the like elongated flexible members.

Difficulty has heretofore been experienced with flexible casings of limited diameter in that insufficient resistance is offered thereby to long1'- tudinal stretching thereof. The tension customarily put on such casings frequently separates the coils or turns thereof to such an extent as to permit leakage of the lubricants out of the casing. When the coils of the casing separate unduly under the tensile or other stresses thereon, the casing fails to give the necessary protection to the shaft or other flexible members housed in the casing, and cannot be depended on to perform its required functions.

Previous attempts to increase the resistance of the casing to longitudinal stretch by constructing the casing of two strands arranged in two layers, while being more or less eificient to resist such stress, has resulted in structures which are too complicated and too expensive for ordinary commercial use.

My invention therefore provides a simple, light, but efficient casing, utilizing a minimum amount of material, which is comparatively easy and inexpensive to manufacture and which is highly resistant to longitudinal extension or stretching.

My invention further provides a flexible casing which while adequately resistant to longitudinal or end stretch, maintains its proper seal between the respective coils to prevent'leakage or loss of lubricants or access of foreign materials to the interior thereof.

My invention further provides a flexible casing made of a pair of strips arranged in edgeadjacent-overlapping relation to form a seal therebetween at all times, one of the strips being of considerable width and wider than the other to offer great resistance to end stretch, the strips being further so arranged that while providing two relatively slidable layers of material at the joints therebetween, the total thickness of the casing is not substantially greater than that of the wider strip only.

fhe various objects of the invention will be 50 clear from the description which follows and from the drawing, in which,

l is a front view and partial section of a portion of a flexible casing embodying my invention.

Fig. 2 is a similar view of the same showing ment of the strips are important features of my j invention.

It will be understood that the strip ID at its inner face I2 is of substantially twice the width of that of the upper face I3 of the strip II,

and of the upper face IQ of the strip Ill. The

strip II being of generally triangular crosssection and the strip Ill of generally trapezoidal cross-section, the area of the cross-section of the strip If! is approximately three times that V of the strip ll. By reason of its excess width,

the strip I0 is highly resistant to end stretch,

while making it possible to maintain the thicknesses of the strips ill and I I, and the consequent thickness of the casing at a minimum. The inner parts of each of the side edges of the strip Iii are preferably rounded as at I5, I6 in arcs of predetermined radius, beginning at points l1 and I8 respectively. At the points I9 and are formed the respective shoulders 2| and 22, the faces of said shoulders being preferably at substantially right angles to the face I2.

The strip II is of generally triangular-crosssectional shape, the outermost face I3 thereof being preferably fiat and being of substantially the same width as the corresponding outermost face I4 of the strip Iii. Extending inwardly from the outer face I3 are the respective shoulders 23, 24 adapted normally to engage the corresponding shoulders 22 and M respectively of the adjacent coils 29, 35) of the strip I0 (Fig. 1). From innermost corners of the shoulders 23 and 24 extend the respective concavely arcuate edges 25, 26 of substantially the same radius as the edges I5 and it of the strip I0 and adapted to overlap said edges and to cooperate therewith to seal the slight space between the faces I2 of the adjacent coils 29, 38 of the strip Ill. The edges 25 and 26 extend to the innermost blunt edge 21 of the strip I I. It will be understood that the coils of said strip II are consequently fitted into and accurately seal the spaces between the adjacent coils of the strip Ill. Said strip II, therefore, serves as a filler and sealing member and presents an outermost surface on the coils thereof of substantially the same width as the surfaces IA of the coils of the main strip, whereby the casing appears to be wound of a single strip of material of substantially the same width throughout.

Nevertheless, it will be understood that even though substantial tension, bending stress and/or flexure is applied to the casing, movement of the shoulder 22 of one of the coils as 29 away from the shoulder 2! of the next coil 39 of the strip,

does not break the seal formed by the strip H,

owing to the overlapping ofthe concavely arcuate edges of the strip H on the convexly arcuate edges of the coils of the strip lil. (See Fig. 2.)

It will further be understood that since the strips If) and H are wound in the form of a helix to provide turns or coils in adjacent relation, the pitch of each of the coils is twice that which the coils would have had if wound from a single strip only.

From the above, it will be noted that by the provision of two helically wound adjacent strips in proper overlapping relation, one strip about twice as Wide as the other, great resistance to end stretch is attained, first, by reason of the increased width of the main strip, and second, by the increase of the pitch of the turns or coils without sacrificing the proper sealing effect of the flller strip and while maintaining the amount of material and the resulting thickness of the casing and the labor of assembling the strips at a minimum.

While I have shown and described a certain specific embodiment of my invention, it will be understoodthat I do not intend to limit myself thereto, but desire to claim my invention as broadly as may be permitted by the state of the prior art and the scope of the appended claims.

I claim:

1. In a flexible helically wound metal casing, a wider strip having an innermost cylindrical face of substantially twice the width of the outermost cylindrical face thereof, and having a thickness less than the width of either of said faces, a convexly arcuate edge portion extending from each of the peripheral edges of said innermost face toward the outermost face of the strip and terminating inwardly thereof, a shoulder extending from the outermost point of said convex portion to said outermost face, and arranged at substantially right angles to said faces, said wider strip being wound in a plurality of turns, and a filler strip having concave edge portions in contact with the convex edge portions of the adjacent coils of said wider strip arranged between said coils, said filler strip being of substantially the same thickness as that of said wider strip and having outermost and innermost faces arranged respectively in the same cylindrical surfaces as those in which the outermost and innermost faces of the wider strip are arranged, and a shoulder on the filler strip arranged at substantially right angles to the faces of the filler strip and normally in contact with the corresponding shoulder of the wider strip, the casing wall formed by said strips being of substantially uniform thickness throughout.

2. In a helicallywound flexible metal'casing, a

pair of helically wound strips arranged in adjacent relation, one of said strips being of generally trapezoidal cross-section and the other being of generally triangular cross-section, the base of the trapezoidal cross-section being substantially twice the width of the: base of the triangular cross-section, said one strip having convexly arcuate edges and said other strip having conaosaeee cavely arcuate edges, said strips having normally contacting shoulders extending inwardly at substantially right angles from the outer faces of the strips to said arcuate edges.

3. In a helically wound flexible metal casing, a pair of flat Wire strips arranged in adjacent relation with their respective inner and outer surfaces in substantial alignment and with the edges thereof overlapping through the greater part of the thickness thereof, one of said strips having an inner face of greater width than the outer face of the other strip and having the edges thereof shaped convexly and terminating in substantially perpendicular shoulders intermediate the faces thereof, the corresponding edges of the other strip being shaped concavely and having corresponding perpendicular shoulders adapted normally to engage the shoulders of said first mentioned strip.

4. In a flexible metal casing of a predetermined substantially uniform thickness of material, a pair of strips arranged in edge-abutting relation with their respective inner and outer faces aligned and helically wound, one of said strips having a thickness equal to said predetermined thickness and being of generally trapezoidal cross-section, the other of said strips being of generally triangular cross-section and of the same thickness, the area of the cross-section of said first mentioned strip being substantially three times the area of the cross-section of the second mentioned strip, said casing being highly resistant to longitudinal stretching.

5. In a flexible casing, a strip Wound helically into a plurality of coils, said strip having a generally trapezoidal cross-section and being provided with edges each having a portion thereof convex and the remainder thereof providing a reentrant substantially right angled shoulder, and a filler strip having edges fitted to and overlapping the edges of said first mentioned strip and sealing the space between the coils thereof, both of said strips having outer exposed faces of substantially equal area lying in the same cylindrical surface.

6. A flexible casing of substantially uniform thickness throughout and having smooth cylindrical and parallel inner and outer surfaces, comprising a strip wound helically into a plurality of coils, said strip having an inner face wider than the outer face thereof, said outer face forming half of the outer surface of the casing, and a filler strip having an outer face of lesser width than the inner face of said first mentioned strip and forming the other half of the outer face of the casing, the respective inner and outer faces of said strips being aligned with each other and cylindrical.

'7. A flexible casing of uniform thickness and highly resistant to end stretch, said casing having an outer smooth and substantially uninterrupted outer surface and a parallel inner surface comprising a main strip wound helically into a plurality of coils, edges on said strip converging from the inner face of said strip toward the outer face thereof, and a filler strip filling and sealing the space between said coils and having an outer face of substantially the same width as and aligned with the outer face of said first mentioned strip, and having edges converging from the outer face thereof toward the inner face.

8. In a-flexible casing, a pair of adjacent strips wound helically into a plurality of coils, each of said strips being of the same thickness as that of the casing and having an outer face of substantially the same width as that of the other strip each to form half of the outer exposed surface of the casing, and one of said strips having an inner face of greater width than that of the outer face to impart to said casing maximum resistance to end stretch.

9. In a flexible casing, a pair of adjacent strips wound into a plurality of double pitch coils, one of said strips having an inner face of greater width than the outer face of either strip, and the other of said strips being of generally triangular cross-section, the corresponding surfaces of the strip being aligned with each other, and both strips being of the maximum thickness as that of the casing.

10. A flexible casing resistant to end stretch and having smooth parallel cylindrical inner and outer faces and being of substantially the same thickness throughout, said casing comprising a pair of flat-wire strips in edge-adjacent relation and each having an outer face of substantially the same width as that of the other, said strips being wound into coils of double pitch, and one of said strips having an inner face of greater width than that of the outer faces, and the other having an inner face of less Width than that of the outer faces.

11. A flexible casing comprising a pair of edgeadjacent flat-wire strips wound into coils of double pitch and having aligned cylindrical outer faces of substantially the same width, the inner face of one of said strips being Wider and the inner face of the other strip being narrower than the outer faces, said strips being of the same thickness and of the same thickness as that of the casing.

12. In a flexible casing, a pair of metallic fiatwire strips having complementary interfitting partly curved adjacent edges, said edges terminating in right-angled shoulders at the outer surfaces of said strips, said strips being arranged in edge-abutting relation and having outer faces of substantially the same width throughout, the inner face of one of said strips being wider and the inner face of the other strip being narrower than'said outer faces.

CHARLES FISCHER. 

